The effect of illumination on the visibility of steps and ramps for people with low vision.

SIGNIFICANCE: Poor visibility of indoor features such as steps and ramps can pose mobility hazards for people with low vision. For purposes of architectural design, it is important to understand how design parameters such as the illumination level of an indoor space affect the visibility of steps and ramps. PURPOSE: This study was aimed to examine the effect of typical variation in photopic illumination level in an indoor space on the visibility of steps and ramps for individuals with low vision. METHODS: Steps and ramps were constructed in a large windowless room illuminated by overhead lights. Subjects with low vision completed a 5-alternative forced choice task to recognize the targets at three levels of photopic illumination, i.e., 800, 80, and 8 lux, and gave confidence ratings about their judgments on a 5-point scale. Acuities and contrast sensitivities of the subjects were also measured at each illumination level. For comparison, a group of normally sighted subjects with simulated acuity reduction also completed the step-and-ramp recognition task. RESULTS: For both groups of subjects, recognition accuracy was not affected by illumination level. For subjects with low vision, however, there was a significant effect of illumination level on confidence rating: subjects became more confident about their judgments with increasing illumination. There was also a weak effect of illumination level on acuity and contrast sensitivity, both worsening with decreasing illumination. Recognition performance was best predicted by contrast sensitivity, whereas confidence was best predicted by visual acuity. CONCLUSIONS: Illumination variation over a typical photopic range in an indoor space had minimal effect on the objective visibility of steps and ramps for people with low vision. However, illumination level affected subjects' confidence in hazard recognition. Design decisions on parameters such as illumination should consider the consequences on both the objective and the subjective accessibility of a space.

Nonreciprocal topological mode conversion by encircling an exceptional point in dynamic waveguides.

The topology of exceptional points (EPs) has been revealed by taking stationary or dynamical encircling around them, which induces eigenstate exchange or chiral mode conversion. However, the conversions are usually reciprocal obeying restricted transmittances. Here we propose the concept of nonreciprocal encircling of EPs in a dynamic waveguide under complex modulation. The waveguide allows direction-dependent EPs in their quasienergy spectra due to different phase-matching conditions for opposite propagation direction. We design a closed loop that will encircle the EP in the backward direction but not in the forward direction. In this way, a nonreciprocal topological conversion is achieved as the forward transmittance from the even to odd mode significantly exceeds the backward transmittance from the odd to even mode. As a result, the forward propagation produces two modes with equal strength while the backward propagation leads to a specific mode regardless of the input. The structure is promising for making robust optical isolators.

Establishment and Reliability Evaluation of Prognostic Models in Diabetic Foot.

Purpose: To study the risk factors affecting amputation and survival in patients with diabetic foot (DF) and to construct a predictive model using the machine learning technique for DF foot amputation and survival and evaluate its effectiveness. Materials and Methods: A total of 200 patients with DF hospitalized in the First Affiliated Hospital of Shantou University Medical College in China were selected via cluster analysis screening, Kaplan-Meier survival calculation, amputation rate and Cox proportional hazards model investigation of risk factors associated with amputation and death. In addition, we constructed various models, including Cox proportional hazards regression analysis, the deep learning method convolution neural network (CNN) model, backpropagation (BP) neural network model, and backpropagation neural network prediction model after optimizing the genetic algorithm. The accuracy of the 4 prediction models for survival and amputation was assessed, and we evaluated the reliability of these computational models based on the size of the area under the ROC curve (AUC), sensitivity and specificity. Results: We found that the 1-year survival rate in patients with DF was 88.5%, and the 1-year amputation rate was 12.5%. Wagner's Classification of Diabetic Foot Ulcers grade, ankle-brachial index (ABI), low-density lipoprotein (LDL), and percutaneous oxygen partial pressure (TcPO2) were independent risk factors for amputation in patients with DF, while cerebrovascular disease, Sudoscan sweat gland function score, glycated hemoglobin (HbA1c) and peripheral artery disease (PAD) were independent risk factors for death in patients with DF. In addition, our results showed that in the case of amputation, the COX regression predictive model revealed an AUC of 0.788, sensitivity of 74.1% and specificity of 83.6%. The BP neural network predictive model identified an AUC of 0.874, sensitivity of 87.0% and specificity of 87.7%. An AUC of 0.909, sensitivity of 90.7% and specificity of 91.1% were found after optimizing the BP neural network prediction model via genetic algorithm. In the deep learning CNN model, the AUC, sensitivity and specificity were 0.939, 92.6%, and 95.2%, respectively. In the analysis of risk factors for death, the COX regression predictive model identified the AUC, sensitivity and specificity as 0.800, 74.1% and 85.9%, respectively. The BP neural network predictive model revealed an AUC, sensitivity and specificity of 0.937, 93.1% and 94.4%, respectively. Genetic algorithm-based optimization of the BP neural network predictive model identified an AUC, sensitivity and specificity of 0.932, 91.4% and 95.1%, respectively. The deep learning CNN model found the AUC, sensitivity and specificity to be 0.861, 82.8% and 89.4%, respectively. Conclusion: To identify risk factors for death, the BP neural network predictive model and genetic algorithm-based optimizing BP neural network predictive model have higher sensitivity and specificity than the deep learning method CNN predictive model and COX regression analysis.

Task-dependent effects of voluntary space-based and involuntary feature-based attention on visual working memory.

Previous research has shown that visual working memory (VWM) can be modulated by space-based or feature-based attentional selection. However, it remains unclear how the two modes of attention operate jointly to affect VWM, and in particular, if involuntary feature-based attention plays a role in VWM. In this study, a pre-cued change detection paradigm was employed to investigate the concurrent effects of space- and feature-based attention on VWM. Space-based attention was manipulated by informative spatial cueing and by varying the proximity between the test item and the cued (fixated) memory item, while feature-based attention was induced in an involuntary manner by having the test item to share the same color or shape with the cued item on a fraction of trials. The results showed that: (1) the memory performance for the cued items was always better than the uncued items, suggesting a beneficial effect of voluntary spatial attention; (2) with a brief duration of the memory array (250 ms), cue-test proximity benefited VWM in the shape judgment task but not in the color judgment task, whereas with a longer duration (1200 ms), no proximity effect was found for either task; (3) VWM was improved for the same-colored items regardless of the task and duration; (4) VWM was improved for the same-shaped items only in the shape judgment task with the longer duration of the memory array. A discrimination task further showed that the proximity effect associated with VWM reflects a perceptual bottleneck in memory encoding for shape but not for color with a brief display. Our results suggest that involuntary feature-based attention could be triggered by spatial cueing to modulate VWM; involuntary color-based attention facilitates VWM independently of task, whereas shape-based facilitation is task-dependent, i.e., confined only to the shape judgment task, presumably reflecting different attention-guiding potencies of the two features.

The transition from feature to object: Storage unit in visual working memory depends on task difficulty.

Visual working memory (VWM) is a cognitive memory buffer for temporarily processing and storing visual information. Previous studies suggest that its capacity is severely limited, and there is an ongoing debate on whether the storage capacity is object-based or feature-based in VWM. In this study, a change-detection task was employed to investigate whether and how task difficulty can affect VWM, specifically, its capacity and the unit of storage. Task difficulty was manipulated through the set size of memory items, memory fidelity required by the resolution of representation and the type of feature tested. We examined two types of stimuli: the single-feature type, where each memory item was composed of a single feature (color or shape), and the conjunctive-feature type, where each item was composed of a conjunction of two features (colored shape). Experiment 1 replicated the previous findings that memory capacity for colors was larger than shapes, and decreased with the resolution demand regardless of the type of stimuli. In Experiment 2, we analyzed and compared the results from single-feature items and conjunctive-feature items in the low- and high-resolution conditions while controlling for the number of to-be-remembered features. By directly matching the estimated capacity based on an object-unit and a feature-unit with the theoretical prediction, the results showed that the unit storage in VWM tended to be feature-based with low task difficulty, and to be object-based with high task difficulty. This suggests that VWM is dynamic and flexible, dependent on the load of the current task.

When the weaker conquer: A contrast-dependent illusion of visual numerosity.

Humans and many nonhuman species have the capacity to perceive the approximate numerosity of a large set of elements. In the visual domain, various factors have been found to affect perceived numerosity, including, as studied here, the effect of luminance contrast. We report a new numerosity illusion in which low-contrast elements appear to be more numerous than high-contrast ones when intermixed in the same display, an effect we have called "the weak conquer the strong." The illusion occurred for both positive and negative contrast disks of the same sign; for example, white disks appeared less numerous than light gray disks when presented on a dark gray field (all positive contrasts). The illusion grew in size as the contrast difference between the two sets of disks became smaller but did not hold for disks with opposite signs, such as white and dark gray disks on a light gray field. The illusion was also eliminated when the disks were segregated spatially, in which case the high-contrast (white) disks and low-contrast (gray) disks appeared equally numerous. The illusion is due to the loss of some high-contrast elements; e.g., the perceived numerosity of the white disks was decreased whereas that of gray ones was preserved as shown by matching to isolated sets of white or gray disks. We speculate that failure in segregation coupled with error in contrast normalization may account for the numerosity illusion.

Saturation and brightness modulate the effect of depth on visual working memory.

Although previous studies show inconsistent results regarding the effect of depth perception on visual working memory (VWM), a recent finding shows that perceptually closer-in-depth items are better remembered than farther items when combining the congruent disparity and relative size cues. In this study, we employed a similar change detection paradigm to investigate the effects of saturation and brightness, alone or in combination with binocular disparity, on VWM. By varying the appearance of the memory items, we aimed to manipulate the visual salience as well as to simulate the aerial perspective cue that induces depth perception. We found that the change detection accuracy was significantly improved for brighter and more saturated items, but not for items solely with higher saturation. Additionally, combining saturation with the congruent disparity cue significantly improved memory performance for perceptually closer items over farther items. Conflicting the disparity cue with saturation eliminated the memory benefit for the closer items. These results indicate that saturation and brightness could modulate the effect of depth on VWM, and both visual salience and depth perception affect VWM possibly through a common underlying mechanism of setting priority for attentional selection.

Simulating visibility under reduced acuity and contrast sensitivity.

Architects and lighting designers have difficulty designing spaces that are accessible to those with low vision, since the complex nature of most architectural spaces requires a site-specific analysis of the visibility of mobility hazards and key landmarks needed for navigation. We describe a method that can be utilized in the architectural design process for simulating the effects of reduced acuity and contrast on visibility. The key contribution is the development of a way to parameterize the simulation using standard clinical measures of acuity and contrast sensitivity. While these measures are known to be imperfect predictors of visual function, they provide a way of characterizing general levels of visual performance that is familiar to both those working in low vision and our target end-users in the architectural and lighting-design communities. We validate the simulation using a letter-recognition task.

DUSP1 Promotes Osimertinib Drug-Tolerant Persistence by Inhibiting MAPK/ERK Signaling in Non-small Cell Lung Cancer.

EGFR tyrosine kinase inhibitors (EGFR-TKIs) are the first-line treatment for EGFR-mutant non-small cell lung cancer (NSCLC) patients, which remarkably improve the clinical outcomes. However, drug resistance has greatly impaired the efficacy of EGFR-TKIs and contributes to cancer treatment failure. DUSP1, a negative regulator of MAPK signaling pathway, was discovered to mediate drug resistance in multiple types of cancers. Our study aimed to explore the role of DUSP1 in NSCLC cell resistance to osimertinib, a third-generation EGFR-TKI. Human NSCLC cell lines PC-9 and HCC827 were exposed to increasing concentrations of osimertinib for over 6 months to generate osimertinib resistant cells (PC-9-OR and HCC827-OR). The viabilities of osimertinib-resistant and parental sensitive NSCLC cells in response to osimertinib stimulation were detected by MTS assay and the IC50 values for osimertinib were obtained. The differentially expressed genes in osimertinib-resistant and sensitive NSCLC cells were identified by analyzing the GEO dataset GSE106765 using bioinformatic tools. DUSP1 expression was knocked down by using the short hairpin RNAs (shRNAs). Then, the effects of DUSP1 silencing on osimertinib-resistant and sensitive NSCLC cell resistance to osimertinib, viability, proliferation and apoptosis were assessed through loss-of-function experiments. The expression of key molecules (JNK, ERK, and p38 MAPK) in the MAPK signaling pathway was detected through western blotting analysis. DUSP1 was overexpressed in osimertinib-resistant NSCLC cells versus parental sensitive cells. DUSP1 silencing attenuated the resistance of NSCLC cells to osimertinib. DUSP1 silencing markedly inhibited osimertinib-resistant and sensitive NSCLC cell proliferation but enhanced cell apoptosis. Mechanically, DUSP1 knockdown increased phosphorylated-JNK, ERK, and p38 MAPK levels in NSCLC cells. Treatment with SB203580, the p38 MAPK inhibitor, reversed the effects of DUSP1 silencing on osimertinib-resistant NSCLC cell resistance to osimertinib, cell proliferation and apoptosis. DUSP1 downregulation restores the sensitivity of NSCLC cells to osimertinib via activating the MAPK signaling pathway.

Odorant Binding Protein Expressed in Legs Enhances Malathion Tolerance in Bactrocera dorsalis (Hendel).

Bactrocera dorsalis is a highly invasive species and is one of the most destructive agricultural pests worldwide. Organophosphorus insecticides have been widely and chronically used to control it, leading to the escalating development of resistance. Recently, odorant binding proteins (OBPs) have been found to play a role in reducing insecticide susceptibility. In this study, we used RT-qPCR to measure the expression levels of four highly expressed OBP genes in the legs of B. dorsalis at different developmental stages and observed the effect of malathion exposure on their expression patterns. The results showed that OBP28a-2 had a high expression level in 5 day old adults of B. dorsalis, and its expression increased after exposure to malathion. By CRISPR/Cas9 mutagenesis, we generated OBP28a-2-/- null mutants and found that they were more susceptible to malathion than wild-type adults. Furthermore, in vitro direct affinity assays confirmed that OBP28a-2 has a strong affinity for malathion, suggesting that it plays a role in reducing the susceptibility of B. dorsalis to malathion. Our findings enriched our understanding of the function of OBPs. The results highlighted the potential role of OBPs as buffering proteins that help insects survive exposure to insecticides.

An Odorant Receptor Expressed in Both Antennae and Ovipositors Regulates Benzothiazole-Induced Oviposition Behavior in Bactrocera dorsalis.

The oriental fruit fly,Bactrocera dorsalis (Hendel), is a notorious pest of fruit crops, causing severe damage to fleshy fruits during oviposition and larval feeding. Gravid females locate suitable oviposition sites by detecting the host volatiles. Here, the oviposition preference of antenna-removed females and the electrophysiological response of ovipositors to benzothiazole indicated that both antennae and ovipositors are involved in perceiving benzothiazole. Subsequently, odorant receptors (ORs) expressed in both antennae and ovipositors were screened, and BdorOR43a-1 was further identified to respond to benzothiazole using voltage-clamp recording. Furthermore, BdorOR43a-1-/- mutants were obtained using the CRISPR/Cas9 system and their oviposition preference to benzothiazole was found to be significantly altered compared to WT females, suggesting that BdorOR43a-1 is one of the important ORs for benzothiazole perception. Our results not only demonstrate the important role of antennae and ovipositors in benzothiazole-induced oviposition but also elucidate on the OR responsible for benzothiazole perception in B. dorsalis.

An Antenna-Enriched Chemosensory Protein Plays Important Roles in the Perception of Host Plant Volatiles in Bactrocera dorsalis (Diptera: Tephritidae).

Olfaction plays indispensable roles in insect behavior such as host location, foraging, oviposition, and avoiding predators. Chemosensory proteins (CSPs) can discriminate the hydrophobic odorants and transfer them to the odorant receptors. Presently, CSPs have been identified in many insect species. However, their presence and functions remain unknown in Bactrocera dorsalis, a destructive and invasive insect pest in the fruit and vegetable industry. Here, we annotated eight CSP genes in the genome of B. dorsalis. The results of quantitative real-time polymerase chain reaction (RT-qPCR) showed that BdorCSP3 was highly expressed in the antennae. Molecular docking and in vitro binding assays showed that BdorCSP3 had a good binding ability to host volatiles methyl eugenol (ME, male-specific attractant) and ß-caryophyllene (potential female attractant). Subsequently, CRISPR/Cas9 was used to generate BdorCSP3-/- mutants. Electroantennograms (EAGs) and behavioral assays revealed that male mutants significantly reduced the preference for ME, while female mutants lost their oviposition preference to ß-caryophyllene. Our data indicated that BdorCSP3 played important roles in the perception of ME and ß-caryophyllene. The results not only expanded our knowledge of the olfaction perception mechanism of insect CSPs but also provided a potential molecular target for the control of B. dorsalis.

The SUMOylation of zinc-fingers and homeoboxes 1 (ZHX1) by Ubc9 regulates its stability and transcriptional repression activity.

Zinc-fingers and homeoboxes protein 1 (ZHX1) belongs to the ZF (zinc-fingers) class of homeodomain transcription factors, and its function remains largely unknown. ZHX1 has been previously found to interact with the activation domain of the nuclear factor Y subunit A (NFYA) and to have a transcriptional repression activity. Here, we report that the SUMO-E2 conjugating enzyme Ubc9 was identified to interact with ZHX1 by an interaction screen using a yeast two-hybrid system. This interaction was confirmed by co-immunoprecipitation and co-localization assays. Further study showed that ZHX1 is SUMOylated by Ubc9 with SUMO1 at the sites K159, K454, and K626. Furthermore, we demonstrated that the SUMOylation of ZHX1 regulated the stability, ubiquitination and transcriptional activity of ZHX1.

Numerosity depends on normalized contrast energy: Review and square-root law model.

The perceived numerosity of many randomly-located items of fixed contrast depends on the integrated contrast energy (CE) of the display. We show here that a model based on √(CE), normalized by contrast amplitude, can fit numerosity judgment data in various tasks and over a wide range of numerosities. The model shows that judged numerosity increases linearly with √(N), where N is the number of displayed items above the subitization range, and can explain: 1) the general underestimation in absolute judgement of numerosity; 2) the contrast independence (constancy) of numerosity judgment in segregated displays, i.e., judged numerosities are not affected by item contrast; 2) a contrast-dependent illusion where the numerosity of higher-contrast items is further underestimated when intermingled with lower-contrast items; and 3) both the threshold and sensitivity of numerosity discrimination between displays of N and M items. The nearly perfect fit of numerosity judgment data by a square-root law over a wide range of numerosities, including the range typically described by Weber's law, but excluding subitization, suggests that normalized contrast energy might be the prevailing sensory code underlying numerosity perception.

Co-expression of soluble guanylyl cyclase subunits and PDE5A shRNA to elevate cellular cGMP level: A potential gene therapy for myocardial cell death.

BACKGROUND: Genetic manipulation on the NO-sGC-cGMP pathway has been rarely achieved, partially due to complexity of the soluble guanylyl cyclase (sGC) enzyme. OBJECTIVE: We aim to develop gene therapy directly targeting the pathway to circumvent cytotoxicity and tolerance after prolonged use of NO-donors and the insufficiency of PDE inhibitors. METHODS: In this study, we constructed lentivirus vectors expressing GUCY1A3 and GUCY1B3 genes, which encoded the α1 and ß1 subunits of soluble guanylyl cyclase (sGC), respectively, to enhance cGMP synthesis. We also constructed lentiviral vector harboring PDE5A shRNA to alleviate phosphodiesterase activity and cGMP degradation. RESULTS: Transductions of human HEK293 cells with the constructs were successful, as indicated by the fluorescent signal and altered gene expression produced by each vector. Overexpression of GUCY1A3 and GUCY1B3 resulted in increased sGC enzyme activity and elevated cGMP level in the cells. Expression of PDE5A shRNA resulted in decreased PDE5A expression and elevated cGMP level. Co-transduction of the three lentiviral vectors resulted in a more significant elevation of cGMP in HEK293 cells without obvious cytotoxicity. CONCLUSION: To the best of our knowledge, this is the first study to show that co-expression of exogenous subunits of the soluble guanylyl cyclase could form functional enzyme and increase cellular cGMP level in mammalian cells. Simultaneous expression of PDE5A shRNA could alleviate feedback up-regulation on PDE5A caused by cGMP elevation. Further studies are required to evaluate the effects of these constructs in vivo.

Two odorant receptors regulate 1-octen-3-ol induced oviposition behavior in the oriental fruit fly.

The oriental fruit fly Bactrocera dorsalis (Hendel) is a notorious pest of fruit crops. Gravid females locate suitable oviposition sites by detecting host plant volatiles. Here, we demonstrate that 1-octen-3-ol, a volatile from mango, guides the oviposition behavior of female flies. Two odorant receptors (BdorOR7a-6 and BdorOR13a) are identified as key receptors for 1-octen-3-ol perception by qPCR analysis, heterologous expression in Xenopus laevis oocytes and HEK 293 cells followed by in vitro binding assays, as well as CRISPR/Cas9 genome editing in B. dorsalis. Molecular docking and site-directed mutagenesis are used to determine major binding sites for 1-octen-3-ol. Our results demonstrate the potential of 1-octen-3-ol to attract gravid females and molecular mechanism of its perception in B. dorsalis. BdorOR7a-6 and BdorOR13a can therefore be used as molecular targets for the development of female attractants. Furthermore, our site-directed mutagenesis data will facilitate the chemical engineering of 1-octen-3-ol to generate more efficient attractants.

fMRI correlates of inhibition of return in perifoveal and peripheral visual field.

When a target appears in the same peripheral location as a previous cue, responding is typically delayed if the cue-target interval is relatively long. This phenomenon is termed inhibition of return (IOR) and has been suggested to reflect an attentional bias in favour of novel visual space. It has been demonstrated recently that IOR is much stronger in the far periphery than in the perifoveal visual field. The present study further investigated the neural mechanisms underlying this eccentricity effect of IOR with an event-related fMRI technique. The results demonstrated a stronger activation in visual cortex for perifoveal processing and a broader activation in multiple brain areas for peripheral processing. When IOR effects were compared between these two areas, a stronger activation of the fronto-parietal network was evidenced for perifoveal versus peripheral IOR, while the prefrontal cortex was more strongly involved in the peripheral IOR versus perifoveal IOR. These results suggest that different neural mechanisms are mediating the dissociable inhibitory functions between the perifoveal and peripheral visual field.

Untypical Contrast Normalization Explains the "Weak Outnumber Strong" Numerosity Illusion.

Less salient, lower contrast disks appear to be more numerous than more salient, higher contrast disks when intermingled in equal numbers into the same display (Lei and Reeves, 2018), but they are equal in perceived numerosity when segregated into different displays. Comparative judgements indicate that the apparent numerosity of the lower contrast disks is unaffected by being intermingled with high contrast disks, whereas the high contrast disks are reduced in numerosity by being intermingled with the low contrast ones (Lei and Reeves, 2018). Here, we report that this illusion also occurs for absolute judgements of the numerosities of displays of from 20 to 80 disks. A model based on luminance-difference contrast normalization (LDCN) explains the illusory loss of high-contrast (salient) items along with veridical perception of the low-contrast ones. The model correctly predicts that perceived numerosity is linearly related to the square-root of the number of disks, with the extent of the illusion depending on an attentionally-weighted function of contrast and assimilation.

Sublethal Dose of ß-Cypermethrin Impairs the Olfaction of Bactrocera dorsalis by Suppressing the Expression of Chemosensory Genes.

The oriental fruit fly, Bactrocera dorsalis, is one of the most destructive fruit insect pests. ß-cypermethrin has been widely used in the orchard to control this major insect. Based on the resistance monitoring in 2011, B. dorsalis developed significant resistance against ß-cypermethrin in fields. This indicated that the B. dorsalis has been exposed to sublethal concentrations of ß-cypermethrin in the field for a long time. Thus, it is urgent to understand the sublethal effects of ß-cypermethrin on this fly to guide the rational use of an insecticide. According to the olfactory preference assays and electroantennogram (EAG) recording, the B. dorsalis after ß-cypermethrin exposure (LD30 = 10 ng/fly) severely decreased the ability to perceive the tested odorants. Moreover, we then performed quantitative real-time PCR and found the chemosensory genes including odorant receptor co-receptor (BdorORco) and ionotropic receptor co-receptors (BdorIRcos) were obviously suppressed. Our results demonstrated that the sublethal dose of ß-cypermethrin impairs the olfaction of the pest insects by suppressing the expression of chemosensory genes (BdorORco and BdorIRcos), which expanded our knowledge of the sublethal effects of the pesticide on insects.

Simulating Visibility and Reading Performance in Low Vision.

PURPOSE: Low vision reduces text visibility and causes difficulties in reading. A valid low-vision simulation could be used to evaluate the accessibility of digital text for readers with low vision. We examined the validity of a digital simulation for replicating the text visibility and reading performance of low-vision individuals. METHODS: Low-vision visibility was modeled with contrast sensitivity functions (CSFs) with parameters to represent reduced acuity and contrast sensitivity. Digital filtering incorporating these CSFs were applied to digital versions of the Lighthouse Letter Acuity Chart and the Pelli-Robson Contrast Sensitivity Chart. Reading performance (reading acuity, critical print size, and maximum reading speed) was assessed with filtered versions of the MNREAD reading acuity Chart. Thirty-six normally sighted young adults completed chart testing under normal and simulated low-vision conditions. Fifty-eight low-vision subjects (thirty with macular pathology and twenty-eight with non-macular pathology) and fifteen normally sighted older subjects completed chart testing with their habitual viewing. We hypothesized that the performance of the normally sighted young adults under simulated low-vision conditions would match the corresponding performance of actual low-vision subjects. RESULTS: When simulating low-vision conditions with visual acuity better than 1.50 logMAR (Snellen 20/630) and contrast sensitivity better than 0.15 log unit, the simulation adequately reduced the acuity and contrast sensitivity in normally sighted young subjects to the desired low-vision levels. When performing the MNREAD test with simulated low vision, the normally sighted young adults had faster maximum reading speed than both the Non-macular and Macular groups, by an average of 0.07 and 0.12 log word per minute, respectively. However, they adequately replicated the reading acuity as well as the critical print size, up to 2.00 logMAR of both low-vision groups. CONCLUSION: A low-vision simulation based on clinical measures of visual acuity and contrast sensitivity can provide good estimates of reading performance and the accessibility of digital text for a broad range of low-vision conditions.